Potentiometer

ABSTRACT

A potentiometer having a resistor which can be adjusted to a desired value by establishing a short circuit between portions of the resistor. The resistor has terminals on both ends. A slider contact which is electrically connected to a slider terminal contacts the resistor and short circuits a portion of the resistor. The slider contact is movable with respect to the resistor. In one embodiment, the slider contact comprises two, spaced-apart, electrically-connected, slider springs carried on a rotatable shaft positioned within a spiral resistor.

United States Patent [191 Gruendinger [111 3,820,052 June 25, 1974 POTENTIOMETER [76] Inventor: Johann Gruendinger, Landstr. l,

8021 Arget, Tegernseer, Germany [22] Filed: Jan. 17, 1973 [21] Appl. No.: 324,383

[30] Foreign Application Priority Data Jan. 25, 1972 Germany 2203431 [52] US. Cl 338/97, 338/137, 338/143 [51] Int. Cl H01c 5/02 [58] Field of Search 338/92, 95, 97, 137, 143-149 [56] References Cited UNITED STATES PATENTS 1,504,483 8/1924 Klopsteg 338/137 X 2,850,606 9/1958 MacLaren 1. 338/149 X 3,191,137 6/1965 Sekerich 338/149 X 3,314,036 4/1967 Kruse 338/143 Primary ExaminerJ. V. Truhe Assistant Examiner-David A. Tone Attorney, Agent, or FirmD. R. Bair; F. M. Arbuckle 5 7 ABSTRACT A potentiometer having a resistor which can be adjusted to a desired value by establishing a short circuit between portions of the resistor. The resistor has terminals on both ends. A slider contact which is electrically connected to a slider terminal contacts the resistor and short circuits a portion of the resistor. The slider contact is movable with respect to the resistor. In one embodiment, the slider contact comprises two, spaced-apart, electrically-connected, slider springs carried on a rotatable shaft positioned within a spiral resistor.

8 Claims, 3 Drawing Figures POTENTIOMETER BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the field of potentiometers and more particularly to a potentiometer having a resistor with terminals on each end, the resistance between the terminals being adjustable by means of a slider contact with short circuits a portion of the resistor.

2. Description of the Prior Art Potentiometers are usually produced in large numbers and are therefore available on the market with only a limited number of fixed resistor values. However, in many applications potentiometers are needed having resistance values deviating from the values available in the mass-produced potentiometers. For ex ample, the total resistance between the terminals of the potentiometer must have a certain value. Occasionally, the length of the slider track or the number of rotations which the slider contact must perform to move over the total resistor do not agree with the required values. For certain applications, multi-turn potentiometers are required whose total resistance between the terminals must be completely covered by a certain number of slider rotations.

Since it is not feasible to adjust the production process for small numbers of particular potentiometers, modifications are made in finished conventional potentiometers in order to adjust them to the desired values. For example, it has been known to provide a shortcircuit connection between one terminal of the potentiometer and a point located between the terminals on the resistor by soldering a connection between the point on the resistor and the terminal. A short-circuit connection of this type makes it possible to reduce the total resistance and to shorten the length of the slider path. Such modification of the resistance values of conventional potentiometers reduces the cost of producing special potentiometers as compared to the cost of producing small quantities of special potentiometers by the conventional mass-production process. However, the price of these potentiometers exceeds the price of mass-produced units.

Another disadvantage of the prior art is the fact that a soldered short-circuit connection between one terminal and a point on the resistor can be obtained only in wire-wound potentiometers. In the case of potentiometers with a resistor film or resistor layer, a modifica .tion of the resistor cannot be obtained in this fashion.

SUMMARY OF THE INVENTION An object of the present invention is to provide a potentiometer having a resistor which can be easily adjusted to desired resistance values deviating from conventional values. Another objective is to provide such a potentiometer utilizing a wire-wound resistor. A further objective is to provide such a potentiometer utilizing resistors which are not wire-wound.

According to the invention, the slider is configured so that is establishes a short circuit between two points on an adjustable portion of the resistor.

A certain portion of the resistor can be shortcircuited in various ways by means of the slider. For example, the width of the slider can be selected to span a portion of the resistor so that only the desired portion of the resistor is short-circuited. Or, adjustable sliders which rest with two contact fingers on the resistor can be used, the distance between the contact fingers being adjustable to short-circuit desired portions of the resistor. By utilizing such a construction, the total resistance of the potentiometer or the range of slider motion can be simply and inexpensively adapted to requirements without additional complications in the production process. Moreover, this construction can be used in any type of potentiometer, including potentiometers with a resistor film.

In a preferred embodiment of the invention, the potentiometer has the form of a multi-turn potentiometer with a spiral resistor. The resistor is mounted around a shaft carrying a slider movable in axial direction on the shaft by rotation of the shaft. The slider comprises two electrically connected, spring-type sliders spaced apart on the shaft a pre-determined axial distance. The axial distance between the two slider springs determines the potentiometer portion which is shunted by a short circuit. Since the two slider springs are moved simultaneously on the shaft, the shunted resistance situated between the two sliders is constant. No extensive modification of prior art potentiometers is required in the production of adaptable potentiometers of this type. A second slider of the type used in conventional potentiometers is simply mounted on the shaft of a conventional potentiometer.

In an alternate embodiment of the multi-turn potentiometer, a slider track is provided on the shaft, the slider track being connected to the slider terminal of the potentiometer and to the two spring-type sliders. A potentiometer of this type is particularly suitable for special purposes since no additional short-circuit connections must be made between the two spring-type sliders, the short circuit connection being formed by the slider track.

In another embodiment, at least two electrically connected slider tracks are mounted on the shaft in offset relationship. The two spring-type sliders to be mounted on the shaft can also be arranged in offset relationship. By utilizing multiple slider tracks, reduced lengths of the resistor can be short-circuited, the amount of reduction in length being in proportion to the number of slider tracks used.

BRIEF DESCRIPTION OF THE DRAWINGS The invention is described with reference to a preferred embodiment shown in the drawings. In the drawings:

FIG. 1 is a cross section of a multi-turn potentiometer of the invention;

FIG. 2 is a cross section along line A-A of the multitum potentiometer shown in FIG. 1; and

FIG. 3 is a schematic representation of the potentiometer of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The potentiometer shown in FIG. 1 is a multi-turn potentiometer with resistor I mounted in the form of a spiral in a housing 2. The ends of resistor 1 are provided with tenninals 3 and 4 protruding from housing 2.

Two sliding members 6 and 6' are mounted in housing 2 on shaft 5 which is located in coaxial position with respect to resistor 1. Sliding members 6 and 6' are ro tated by shaft and can move in axial direction on shaft 5. Slider springs 7 and 7', carried by the sliding members, rest on resistor 1. Guiding extensions 8 and 8 are provided'on sliding members 6 and 6'. The guiding extensions surround a portion of a resistor turn and cause the slider springs to slide over resistor 1 when the shaft is rotated. An axial slider track 9 is provided on shaft 5 and is connected to slider springs 7 and 7 via an extension 10. A slider ring 1 l is mounted on the front side of shaft 5. Another sliding spring 12, which is connected to slider terminal 13 protruding from housing 2 of the potentiometer, is in contact with slider ring 11.

As shown in the cross section of FIG. 2, sliding members 6 and 6 are nonrotatably mounted on shaft 5. Additionally, FIG. 2 shows the connection of resistor l with slider track 9 on the shaft by means of slider spring 7.

A short-circuit connection between the two slider springs 7 and 7 is obtained by means of extensions and slider track 9 mounted on shaft 5. The resistor portion situated between slider springs 7 and 7 is therefore shunted by the short-circuit connection. Consequently, the total resistance appearing between terminals 3 and 4 of the potentiometer consists of the partial resistances beyond the short-circuited portion, denoted by R1 and R2 in FIG. 3. Since the two sliding members 6 and 6' and the slider springs 7 and 7' move uniformly when shaft 5 is rotated, the shortcircuited portion of the resistor and, hence, the sum of resistances R1 and R2 remain constant. When only one slider is used, the potentiometer is of the type of conventional l0-turn potentiometers. However, in the embodiment shown with two slider springs 7, 7 mounted on shaft 5, the potentiometer functions like a six-turn potentiometer, since the slider range extends only over six turns, with the four other turns being short-circuited.

A potentiometer of this type is easily assembled. In contrast to the assembly of a conventional IO-turn potentiometer, two sliding members, rather than one sliding member, are mounted on shaft 5. The resistor portion to be short-circuited by slider springs 7, 7' is obtained by screwing the first sliding member 6 over a desired number of turns into housing 2, with sliding member 6' abutting resistor l and being adjusted by means of guiding extensions 8. Next, the second sliding member 6 is brought into engagement with the first turn of the resistor and screwed into the proper position.

The invention is not restricted to the embodiment shown but can be applied to any type of potentiometer. The two slider springs need not necessarily be separated. Rather, a single slider of selected width can be used, the width selected depending upon the resistance value of theresistor section to be short-circuited. Particularly in the case of trimmer potentiometers (which consist of an annular film resistor over which a slider spring rotates), it is convenient to mount two slider springs on a common shaft and to provide an adjustable angular spacing between the two slider springs.

In multi-tum potentiometers, resistor sections which do not correspond to one full turn or to an integer multiple of slider rotations can be short-circuited by providing several slider tracks on the periphery of the shaft and mounting the slider springs in offset relationship on the shaft. It is also convenient to provide the sliding members with a guiding lug which runs along the shaft. Additionally, slider springs of different length can be arranged on the sliding member so that the slider springs rest on peripheral resistor points in offset relationship, or the slider springs can be made peripherally adjustable so that resistor intervals of any length can be short-circuited.

What we claim is: I l. A potentiometer comprising: a resistor element having terminals on two ends thereof; a slider contact contacting said resistor element and short-circuiting a portion of said resistor element,

a shaft whose axis is positioned adjacent said resistor element,

said slider contact being carried by said shaft and being movable with respect to said resistor element by rotation of said shaft; and

a slider terminal electrically connected to said slider contact,

said slider contact comprising two spacedapart electrically-connected slider springs contacting said resistor element so that the portion of said resistor element between said slider springs is shortcircuited.

2. The potentiometer as claimed in claim 1, wherein: said resistor element comprises a multi-turn spiral resistor; said shaft is positioned within said spiral resistor in coaxial relation with said spiral resistor; and said slider contact is movable in the axial direction by rotation of said shaft.

3. The potentiometer as claimed in claim 2, wherein said two slider springs are spaced a given axial distance from each other.

4. The potentiometer as claimed in claim 2 including a slider track positioned along a portion of the length of said shaft, said slider track being electrically connected to said slider terminal and contacting said slider contact.

5. The potentiometer as claimed in claim 3, including a slider track positioned along a portion of the length of said shaft; and wherein: said slider contact comprises two, spaced-apart, slider springs, said slider track being electrically connected to said slider terminal and contacting said two slider springs.

6. The potentiometer as claimed in claim 1 wherein said two slider springs are spaced a given circumferential distance from each other.

7. The potentiometer as claimedin claim 6 including two slider tracks positioned along portions of the length of said shaft and peripherally spaced from each other, said two slider tracks being electrically connected to each other, one of said slider tracks contacting one of said slider springs, and the other of said slider tracks contacting the other of said slider springs.

8. A potentiometer comprising:

a multi-turn spiral resistor element having terminals on two ends thereof;

a rotatable shaft positioned along the axis of said spiral resistor element;

two electrically connected sliders spaced a given axial distance from each other, said sliders contacting said resistor element and short-circuiting a portion of said resistor element, and being carried by said shaft so as to be movable along said axis by rotation of said shaft;

a slider terminal electrically connected to said sliders; and

a slider track positioned along a portion of the length of said shaft, said slider track being electrically connected to said slider terminal and contacting said sliders. 

1. A potentiometer comprising: a resistor element having terminals on two ends thereof; a slider contact contacting said resistor element and shortcircuiting a portion of said resistor element, a shaft whose axis is positioned adjacent said resistor element, said slider contact being carried by said shaft and being movable with respect to said resistor element by rotation of said shaft; and a slider terminal electrically connected to said slider contact, said slider contact comprising two spaced-apart electricallyconnected slider springs contacting said resistor element so that the porTion of said resistor element between said slider springs is short-circuited.
 2. The potentiometer as claimed in claim 1, wherein: said resistor element comprises a multi-turn spiral resistor; said shaft is positioned within said spiral resistor in coaxial relation with said spiral resistor; and said slider contact is movable in the axial direction by rotation of said shaft.
 3. The potentiometer as claimed in claim 2, wherein said two slider springs are spaced a given axial distance from each other.
 4. The potentiometer as claimed in claim 2 including a slider track positioned along a portion of the length of said shaft, said slider track being electrically connected to said slider terminal and contacting said slider contact.
 5. The potentiometer as claimed in claim 3, including a slider track positioned along a portion of the length of said shaft; and wherein: said slider contact comprises two, spaced-apart, slider springs, said slider track being electrically connected to said slider terminal and contacting said two slider springs.
 6. The potentiometer as claimed in claim 1 wherein said two slider springs are spaced a given circumferential distance from each other.
 7. The potentiometer as claimed in claim 6 including two slider tracks positioned along portions of the length of said shaft and peripherally spaced from each other, said two slider tracks being electrically connected to each other, one of said slider tracks contacting one of said slider springs, and the other of said slider tracks contacting the other of said slider springs.
 8. A potentiometer comprising: a multi-turn spiral resistor element having terminals on two ends thereof; a rotatable shaft positioned along the axis of said spiral resistor element; two electrically connected sliders spaced a given axial distance from each other, said sliders contacting said resistor element and short-circuiting a portion of said resistor element, and being carried by said shaft so as to be movable along said axis by rotation of said shaft; a slider terminal electrically connected to said sliders; and a slider track positioned along a portion of the length of said shaft, said slider track being electrically connected to said slider terminal and contacting said sliders. 